Various forming systems for a hardenable material, such as concrete, and methods have heretofore been utilized when constructing foundation walls and the like. Such prior forming systems and methods, however, are beset with one or more of the following shortcomings: (a) the forming system is constructed at the site and requires an inordinate amount of manual labor, (b) the method of construction is awkward and time-consuming; (c) the forming system must be disassembled and removed from the site when the wall material has reached a hardened state; (d) if the form units comprising the system are factory assembled they cannot assume a collapsed state when being shipped to the construction site; (e) the various components comprising the system are of costly, bulky, and heavy construction; and (f) special procedures and materials must be utilized after the wall panels have been removed in order to provide adequate thermal insulation and a moisture barrier for the formed wall.